JP6229143B2 - Flow measuring device - Google Patents

Description

  The present invention relates to a flow rate measuring device that measures a flow rate by using ultrasonic waves, and more particularly to a structure having a recess between the ultrasonic transducer and a measurement channel.

  2. Description of the Related Art Conventionally, as this type of flow rate measuring apparatus, an apparatus in which an ultrasonic transmission film is disposed between an ultrasonic transducer and a measurement channel is known (see, for example, Patent Document 1).

  FIG. 7 is an exploded perspective view of the flow rate measuring device described in Patent Document 1.

  As shown in the figure, the flow rate measuring device 101 includes a flow path body 102 and a sensor block 103.

  The flow channel main body 102 is configured to be divided into a plurality of flat flow channels by inserting a plurality of partition plates 105 into a flow channel 104 having a rectangular cross section.

  A first ultrasonic transducer 106 and a second ultrasonic transducer 107 are attached to the sensor block 103. An ultrasonic transmission film 108 is disposed between the ultrasonic transducers 106 and 107 and the flow path 104. This ultrasonic transmission membrane is integrally formed of a mesh member or the like.

  FIG. 8 is a vertical sectional view in the flow direction of the flow rate measuring device shown in FIG.

  As shown in the figure, a first dent 109 and a second dent 110 are formed between the first ultrasonic transducer 106, the second ultrasonic transducer 107, and the flow path 104. .

  In this configuration, the ultrasonic wave emitted from the first ultrasonic transducer 106 passes through the ultrasonic transmission film 108 via the first recess 109 and is then reflected by the bottom surface 111 of the flow path 104. After that, after passing through the ultrasonic transmission film 108 again, the second ultrasonic transducer 107 is reached via the second depression 110. The flow rate of the fluid passing through the flow path 104 is measured based on the propagation time during this period.

JP 2011-112377 A

  However, in the conventional configuration, when the ultrasonic wave passes through the ultrasonic transmission film 108, the ultrasonic wave is attenuated and the reception sensitivity is lowered.

  In this case, the received waveform cannot be accurately captured. Therefore, the measurement accuracy of the propagation time is lowered, and the accurate flow rate measurement is hindered.

The present invention solves the above-mentioned conventional problems, and uses an entrainment flow suppression sheet having an opening instead of an ultrasonic transmission film. This aims to reduce ultrasonic attenuation, improve reception sensitivity, and realize accurate flow measurement.

  The flow rate measuring device of the present invention is arranged to dispose of an ultrasonic wave by disposing an entrainment flow suppression sheet having an opening between a hollow portion in front of a pair of ultrasonic transducers and a measurement channel. Since the number can be reduced, the reception sensitivity can be improved and accurate flow rate measurement can be realized.

Configuration diagram of a flow rate measuring device according to Embodiment 1 of the present invention 1 is an exploded perspective view of a flow rate measuring device according to Embodiment 1 of the present invention. AA 'arrow sectional view of FIG. The top view of the flow suppression sheet | seat in Embodiment 1 of this invention The top view of the flow suppression sheet | seat in Embodiment 2 of this invention The top view of the flow suppression sheet | seat in Embodiment 3 of this invention An exploded perspective view of a conventional flow rate measuring device Vertical sectional view of the flow direction of the flow path block in FIG.

According to a first aspect of the present invention, there is provided a measurement channel having a rectangular cross section, a pair of ultrasonic transducers disposed on one side of the measurement channel, and connected to the measurement channel via a depression, and the pair of ultrasonic channels Propagation time measuring means for measuring the propagation time between the acoustic transducers, and a flow rate calculating means for calculating a flow rate based on the flow velocity obtained from the propagation time measured by the propagation time measuring means, the depression wherein possess arranged an entrainment flow suppression sheet having an opening between the measurement flow path, the opening, by being set to a size such as to limit the recess, ultrasonic Since it is possible to suppress the occurrence of an error due to the entanglement flow of the hollow portion in a state where the attenuation of the flow rate is small, accurate flow rate measurement can be realized.

  In particular, the second invention is more accurate because it is possible to further suppress the entrainment flow in the recess by having the crosspiece at the opening of the entrainment flow restraining sheet of the first invention. Can be realized.

  The third invention is particularly configured to have a lattice portion at the opening of the entrainment flow restraining sheet of the first invention, thereby dividing and restraining the entrainment flow of the recess portion into a lattice shape. Therefore, more accurate flow rate measurement can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the present embodiment.

(Embodiment 1)
The first embodiment will be described with reference to FIGS. 1 is a configuration diagram of a flow rate measuring apparatus according to Embodiment 1 of the present invention, FIG. 2 is an exploded perspective view of FIG. 1, and FIG. 3 is a cross-sectional view taken along arrow AA ′ of FIG.

  In FIG. 1, the flow rate measuring device 1 includes a flow path block 2 and an ultrasonic transducer block 3.

  In FIG. 2, the flow path block 2 is configured to be divided into a plurality of layered flow paths by inserting a plurality of partition plates 5 b into a plurality of grooves 5 a provided in a measurement flow path 4 having a rectangular cross section. Yes.

The ultrasonic transducer block 3 includes a first ultrasonic transducer 6 and a second ultrasonic transducer 7.
Is attached.

  An entrainment flow suppression sheet 8 (hereinafter referred to as a flow suppression sheet) is disposed between the flow path block 2 and the ultrasonic transducer block 3. The flow suppression sheet 8 has a first opening 9 and a second opening 10.

  Further, the flow suppression sheet 8 is disposed on the upper part of the plurality of partition plates 5b and is formed so as to be pressed and sandwiched by the ultrasonic transducer block 3.

  In FIG. 3, a first dent 11 and a second dent 12 are formed between the first ultrasonic transducer 6, the second ultrasonic transducer 7, and the measurement channel 4. Has been.

  And the ultrasonic wave emitted from the 1st ultrasonic transducer 6 passes through the 1st opening part 9 of the flow suppression sheet 8 via the 1st hollow part 11, and is measured by the path | route a. After reaching the bottom surface portion 13 of the flow path 4, the bottom surface portion 13 is reflected, and then passes through the second opening 10 of the flow suppressing sheet 8 by the path b, and then passes through the second depression 12. In this configuration, the second ultrasonic transducer 7 is reached.

  In such a configuration, a propagation time measuring means (not shown) that further measures the propagation time of ultrasonic waves, and a flow rate calculating means (not shown) that calculates the flow rate based on the flow velocity obtained from the propagation time, Flow measurement is performed.

  Next, flow measurement using ultrasonic waves will be described with reference to FIG.

  Let V be the flow velocity of the fluid flowing through the measurement channel 4, C be the speed of sound in the fluid, and θ be the angle between the direction in which the fluid flows and the direction of ultrasonic propagation until the ultrasonic waves are reflected by the bottom surface portion 13. Also, let L be the effective length of the propagation path of the ultrasonic wave that propagates between the first ultrasonic transducer 6 and the second ultrasonic transducer 7.

  At this time, the propagation time t1 until the ultrasonic wave emitted from the first ultrasonic transducer 6 reaches the other second ultrasonic transducer 7 is expressed by the following equation.

t1 = L / (C + Vcos θ) (1)
Next, the propagation time t2 until the ultrasonic wave emitted from the second ultrasonic transducer 7 reaches the other first ultrasonic transducer 6 is expressed by the following equation.

t2 = L / (C−Vcos θ) (2)
When the sound velocity C of the fluid is eliminated from the equations (1) and (2), the following equation is obtained.

V = L / (2cos θ ((1 / t1) − (1 / t2))) (3)
As can be seen from equation (3), if L and θ are known, the flow velocity V is obtained using the propagation times t1 and t2 measured by the propagation time measuring means (not shown).

  Next, as shown in the following equation, the overall flow rate Q is calculated by multiplying the flow velocity V by the cross-sectional area S of the measurement flow path 4.

Q = V x S (4)
However, in general, the measured flow velocity V is different from the overall average flow velocity Vave of the measurement flow path 4, so that the actual flow rate Qt is obtained by multiplying the flow rate Q by a correction coefficient k as shown in the following equation. Ask.

Qt = k x Q (5)
FIG. 4 is a plan view of the flow restraining sheet of the first embodiment.

  The first opening 9 and the second opening 10 opened in the flow suppression sheet 8 have openings having widths w1 and w2 and lengths L1 and L2, respectively. Usually, w1 and w2 are equal, and are equal to the width w of the measurement channel 4 as shown in FIG. L1 and L2 are also equal.

  The opening shape of the 1st hollow part 11 and the opening shape of the 2nd hollow 12 when the flow suppression sheet 8 is seen from the direction of the path | route a and the path | route b by the side of the measurement flow path 4 are shown with the dashed-dotted line. The 1st opening part 9 and the 2nd opening part 10 are set as the magnitude | size which restrict | limits the 1st hollow part 11 and the 2nd hollow 12, respectively.

  The operation and action of the flow rate measuring apparatus configured as described above will be described below.

  In FIG. 3, the flow F to be measured flowing through the measurement flow path 4 is in the vicinity of the first opening 9 and the second opening 10 due to the viscosity of the fluid, the first depression 11 and the second depression. 12 form vortices p, q.

  Since the ultrasonic wave emitted from the first ultrasonic transducer 6 passes through the first opening 9 and the second opening 10 that are free from obstacles, the second ultrasonic wave 6 is not attenuated significantly. To the ultrasonic transducer 7. However, since the ultrasonic wave passes through the first depression 11 and the second depression 12, the flow velocity measured by the ultrasonic wave includes a flow velocity component due to the vortex. Therefore, if the flow velocity component (Δvp, Δvq) due to the vortex is larger than the flow velocity (V) of the measurement channel 4 to be originally measured, this will occur as an error.

  FIG. 4 is a plan view of the flow suppressing sheet.

  As shown in FIG. 4, the flow suppression sheet 8 has a first opening 9 and a second opening 10 that have a first depression 11 and a second depression 12, respectively. Since it is set so as to be restricted, the vortex flows p and q are restricted as compared with the case where the flow suppressing sheet 8 is not provided.

  Then, by setting the lengths L1 and L2 in the first opening 9 and the second opening 10, the flow velocity generated by the vortices p and q is determined as shown in the following formula. If it is set to a predetermined ratio or less with respect to the flow velocity, it becomes possible to suppress an error due to the hollow portion to a predetermined accuracy (m) or less.

(Δvp + Δvq) / V <m (6)
As described above, according to the present embodiment, by using a flow suppressing sheet that can pass ultrasonic waves and has an opening that suppresses the generation of eddy currents, attenuation of ultrasonic waves while ensuring necessary accuracy. Can be reduced.

(Embodiment 2)
FIG. 5 shows a plan view of the flow restricting sheet according to the second embodiment of the present invention.

  In FIG. 5, the first opening 9a and the second opening 10a of the flow restricting sheet 8a have a first vertical beam portion 14 and a second vertical beam portion 15, respectively. The opening 9a and the second opening 10a are divided in the flow direction.

  Other than these structures are the same as those in the first embodiment, and thus are omitted.

  The operation and action of the flow rate measuring apparatus configured as described above will be described below.

  As shown in FIG. 5, the flow restricting sheet 8a has a first vertical beam portion 14 and a second vertical beam portion 15 in the first opening 9a and the second opening 10a, respectively. Therefore, the formation of the vortex flows p and q in the first depression 11 and the second depression 12 due to the flow to be measured in the measurement channel 4 is weakened or divided.

  Thereby, compared with Embodiment 1, the magnitude | size of an error becomes still smaller and an accurate measurement is performed.

(Embodiment 3)
FIG. 6 shows a plan view of the flow restricting sheet according to the third embodiment of the present invention.

  In FIG. 6, the first opening 9 b and the second opening 10 b of the flow suppressing sheet 8 b are further added to the first horizontal crosspiece 16 and the second horizontal crosspiece, respectively, in addition to the second embodiment. Accordingly, the first opening 9b and the second opening 10b are divided in the direction perpendicular to the flow in addition to the flow direction.

  In this case, the first vertical crosspiece portion 14 and the first horizontal crosspiece portion 16 form a first lattice portion 18, and the second vertical crosspiece portion 15 and the second horizontal crosspiece portion 17 Two lattice portions 19 are formed.

  Other than these structures are the same as those in the first embodiment, and thus are omitted.

  The operation and action of the flow rate measuring apparatus configured as described above will be described below.

  As shown in FIG. 6, the flow suppression sheet 8b includes a first vertical beam portion 14 and a second vertical beam portion 15 in the first opening 9b and the second opening 10b, respectively. Since the first horizontal crosspiece 16 and the second horizontal crosspiece 17 are provided, the first depression 11 due to the flow to be measured in the measurement flow path 4 and the vortex p in the second depression 12, The formation of q is weakened or it is divided in the direction perpendicular to the flow.

  Thereby, compared with Embodiment 2, the magnitude | size of an error becomes still smaller and a measurement with a sufficient precision will be performed.

  As described above, since the flow rate measuring device according to the present invention can guarantee measurement accuracy in a state where the attenuation of ultrasonic waves is small, it can be widely applied to gas meters and devices that perform measurement with low power consumption. is there.

DESCRIPTION OF SYMBOLS 1 Flow measuring device 4 Measurement flow path 6 1st ultrasonic transducer 7 2nd ultrasonic transducer 8, 8a, 8b Entrainment flow suppression sheet (flow suppression sheet)
9, 9a, 9b 1st opening part 10, 10a, 10b 2nd opening part 11 1st hollow part 12 2nd hollow part 14 1st vertical crosspiece (crosspiece)
15 Second vertical crosspiece (crosspiece)
18, 19 lattice part

Claims (3)

A rectangular cross-section measurement channel;
A pair of ultrasonic transducers arranged on one side of the measurement flow path and connected to the measurement flow path via a depression;
A propagation time measuring means for measuring a propagation time between the pair of ultrasonic transducers;
A flow rate calculating means for calculating a flow rate based on a flow velocity obtained from the propagation time measured by the propagation time measuring means,
Possess the entrainment flow suppression sheet having the opening provided between the measurement flow path and the recess portion,
The flow rate measuring device in which the opening is set to have a size that limits the depression .  The flow rate measuring device according to claim 1, wherein the flow rate measuring device is configured to have a crosspiece at an opening of the entrainment flow suppression sheet. The flow rate measuring device according to claim 1, wherein the flow rate measuring device is configured to have a lattice portion at an opening of the entrainment flow suppression sheet.

Images